a. Field of the Invention
This invention relates to a closure cap for a container and a method for using the closure cap and container to allow aseptic collection and processing of blood plasma.
B. Background of the Invention
Blood plasma is conventionally collected in a container, such as disclosed in U.S. Pat. No. 3,545,671, which is adapted to receive whole blood directly from a donor and to permit immediate fractionation of the blood into component parts. Following separation, the blood plasma is expressed into a flexible polyvinyl chloride shipping container which may then be placed in a freezing bath to freeze the plasma so as to protect it from deterioration until it can be processed. When the shipping container is received at a central processing plant, it is slit open with a knife to allow the plug of frozen plasma to drop into a vat. After many such plugs have been collected in the vat, processing begins.
There are several problems associated with a system of this type. The major problem is one of bacterial contamination of the plasma at the time the bag is cut with a knife and the blade comes in contact with plasma. Since the same knife is used repeatedly, it can become contaminated by bacteria in the environment. In addition, although the interior of the bag is sterile, the outside is not and may have become contaminated at any stage from the time plasma was introduced into it, during shipping, or at any other time prior to its being cut open. As the frozen plug of plasma slips from the cut bag, the plug can come in contact with the exterior of the bag and thus become contaminated. Another problem associated with this system is that plasma gets trapped in the corners of the bag. Whereas most of the plasma plug is removed, these trapped pockets of plasma do not drop out from the cut bag so that some loss of plasma results. Still another problem is that the bag containing the frozen plasma does not have a uniform shape which could lend itself to adaptation to an automatic bag-opening procedure. Each bag must be manually cut open. This is time-consuming and more expensive.
The conventional system is also undesirable because polyvinyl chloride (PVC) material, of which the flexible shipping containers are formed, must contain a considerable amount of plasticizers in order to give the bag its pliable, flexible characteristic. Since PVC plasticizers are leachable into the blood plasma, use of PVC may have undesirable effects on the plasma. Also, use of PVC containers precludes sterilization with a gaseous sterilizer such as ethylene oxide or formaldehyde since such gases are retained and only slowly released by PVC.
It has generally been known in the past to maintain medical equipment of various kinds in a sterile condition by placing an overwrap formed of flexible plastic around the equipment to form a protective barrier. One such approach disclosed in U.S. Pat. No. 3,468,471 issued to Linder on Sept. 23, 1969, includes the use of a plastic overwrap (bag 10) having a gas permeable bacterial filter, wherein an article placed in the overwrap, may be subjected to a gas sterilization step in which the sterilization gas is allowed to escape through the bacterial filter. A similar technique is disclosed in U.S. Pat. No. 2,204,683 wherein a container is sterilized and sealed by a cover which is in contact with the container during the sterilization process. While these conventional sterilization methods are well suited for some purposes, such methods do not satisfy the stringent requirements imposed by the need for an inexpensive method of asceptically collecting, shipping and processing blood plasma. For example, use of a flexible overwrap such as disclosed in U.S. Pat. No. 3,468,471 would not prevent contamination of the interior of a plasma shipping container unless the container were sealed at the time the overwrap is ruptured. To sterilize and seal a container before inserting the container into an overwrap for subsequent sterilization as disclosed in U.S. Pat. No. 3,468,471 would require an expensive and impractical two step sterilization method.
Also well known in the prior art are closures for rigid containers which allow air to enter the container at the same time that liquid is being withdrawn. One example of such a closure is disclosed in U.S. Pat. No. 3,746,000 which illustrates, in FIG. 1, a closure system 2 having one projection for connection with a conduit for withdrawing liquid from the container and a second projection for permitting air to enter the container. U.S. Pat. No. 2,812,117 discloses a somewhat similar closure including a filter for filtering the air entering the container. U.S. Pat. Nos. 3,480,172 and 2,314,167 are exemplary of techniques for sealing closures having a pair of passageways for both air and liquid. While the conventional closures illustrated in these patents are well suited for many purposes, the disclosed closures do not suggest solution of any of the specific problems relating to plasma processing as outlined above.